B3.2 Structural Systems Applications and Selection

Finite Element Analysis (FEA)

A computerised simulation method that breaks down a model into small elements to analyse how it responds to physical forces.

What FEA Shows

Stress concentration areas (visualised with colour maps)

Interpreting FEA Data

Focus on areas with stress concentrations or unexpected deformations

Force Diagram (Free-Body Diagram)

A diagram showing all forces acting on a structure or object

Key Principles of Force Diagrams

Forces are vectors with magnitude and direction; forces in the same direction add up

Newton's 2nd Law in Structures

Force equals mass times acceleration (F = m × a); if acceleration is zero

Three Steps to Read a Force Diagram

1. Find the loads (arrows pushing down)

Following the Load Path

Tracing a load from where it is applied to the ground to determine which parts are carrying weight and whether they are in tension

Safety Factor (SF) Formula

Ultimate load (or stress) divided by working or allowable load (or stress).

Ultimate Load

The maximum load or stress at which the structure actually fails.

Allowable / Working Load

The load or stress the structure is designed to carry in normal everyday use.

Maximum Intended Load

The total weight of all persons

Dead Loads (Design Load)

Permanent forces such as the weight of the structure itself.

Live Loads (Design Load)

Temporary forces such as people

Environmental Loads (Design Load)

Natural forces from wind

Design Load Formula

Maximum intended load multiplied by the Safety Factor.

Stress Calculation Formula

σ = F / A (Force divided by cross-sectional area)

Strain Calculation Formula

ε = ΔL / L₀ (Change in length divided by original length)

Area Conversion for Calculations

1 mm² equals 0.000001 m² (10⁻⁶ m²)